Print mutexes held in Thread::Dump.

Should help finding and fixing thread suspend timeout issues.

Bug: 15328839
Change-Id: I30a10529cec0716c7571a0318e9f66be54734fd8
diff --git a/runtime/gc/heap.cc b/runtime/gc/heap.cc
index a962f06..45db4a6 100644
--- a/runtime/gc/heap.cc
+++ b/runtime/gc/heap.cc
@@ -2452,7 +2452,7 @@
 }
 
 size_t Heap::GetPercentFree() {
-  return static_cast<size_t>(100.0f * static_cast<float>(GetFreeMemory()) / GetTotalMemory());
+  return static_cast<size_t>(100.0f * static_cast<float>(GetFreeMemory()) / GetMaxMemory());
 }
 
 void Heap::SetIdealFootprint(size_t max_allowed_footprint) {